Insulating composition and method of application



United States Patent 3,468,687 INSULATING COMPOSITION AND METHOD OF APPLICATION Neil L. Thomas, Melbourne, Australia, assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 19, 1965, Ser. No. 441,367 Claims priority, appligation Australia, Mar. 24, 1964,

Int. Cl. C09d 3/5 4; C'08h 17/04, 13/00 US. Cl. 106-281 3 Cl The present invention relates to insulating compositions and processes applicable to subterranean structures and particularly, though not exclusively, to insulating compositions and processes suitable for application to pipelines.

The term pipeline is used hereinafter, for the sake of brevity, to include all subterranean structures.

When insulating pipelines, the following conditions have to be met by the proposed insulating material:

It has now been found that these conditions can be met by employing an insulating composition in accordance with the present invention which comprises an expanded mineral aggregate having a dry density of 45 to 60 pounds per cubic foot mixed with a bitumen, having a ring and ball softening point of 110 F. to 285 F.

Preferred proportions are approximately %-20% by weight of bitumen and 90%-80% by weight of mineral aggregate.

The expanded mineral aggregate is preferably a sintered shale which has been heated to a high temperature, e.g. about 2000" F. Typical properties of suitable expanded shales are as follows:

Particle size:

Below Ms" 1/8 I! II %I! I! A particularly preferred kind of expanded shale is that which is produced by sintering of crushed shale so as to produce individual expanded shale particles consisting of a sintered envelope or outer layer surrounding a cellular core. Appropriately sized oil shale from which the kerogen has been substantially removed (spent shale) is also quite suitable.

The bitumen is preferably a blown or residual bitumen. A residual bitumen having a softening point of 110 F. to 130 F. is suitable in the case of pipelines carrying heated or refrigerated liquids. A blown bitumen with a softening point of 265 F. to 285 F. is preferable in the case of a pipeline carrying liquids heated above 200 F.

The present invention also includes a process for insulating a pipeline which comprises surrounding the pipeline with a composition as defined above at a temperature at which this composition is plastic and thereafter compacting the composition around the pipeline until the density of the composition approximately equals or is greater than that of water (water in this context means primarily water present in the soil; this may be brackish water with a density somewhat above 1 gram/cc) The pipeline is preferably given a priming coat of hitumen before applying the insulating composition of the Density (lbs/ft?) 59 3,468,687 Patented Sept. 23, 1969 ICC present invention and for this purpose the same bitumen as used in the composition is particularly suitable.

A preferred process of making an insulating composition and of insulating a pipeline in accordance with the present invention comprises heating the bitumen component of the insulating composition to a temperature between 200 F. and 500 F., within which limits it is liquid and free-flowing, mixing the mineral aggregate with the bitumen, while maintaining the temperature within this range (e.g. by using a conventional mixer such as is employed for making hot mixes for road construction), placing the resulting mixture while still plastic around the previously primed pipeline and then mechanically compacting the composition.

Normally a trench will first be excavated, a layer of, say, 6 inches of the plastic insulating composition (more or less according to the diameter of the pipeline and the degree of insulation required) will be placed in the bottom of the trench; the pipeline will then be placed on the composition layer, further amounts of composition will be added to surround the pipeline, the whole of the composition will then be compacted and finally the trench will be backfilled.

Other equally effective methods of placing the composition will be readily apparent to those skilled in the art.

The use of conventional machinery and the nature of the insulating composition of the present invention enable pipelines to be insulated in an exceptionally economrc manner.

The mixing of the mineral aggregate with the liquid bitumen and the application of the mixture while still hot ensures sealing and waterproofing of the individual particles of the aggregate and also the waterproofing and protection of the pipeline against corrosion, especially when priming of the pipeline is carried out.

A typical insulating composition in accordance with the present invention is as follows:

Material Grade Wt. percentage Fine aggregate minus 30-50 Medium aggregate 15-25 Coarse aggregate- 3545 Bitumen 10-20 added The invention is further illustrated by the following specific example of an insulating composition and its application to a pipeline in accordance with the present invention.

An insulation composition was manufactured according to the following table:

Material: Weight Percentage Expanded shale-Fine /a", no dust) 38 Expanded shaleMedium (Mf') l8 Expanded shaleMedium /2") 38 Expanded shale-Coarse 8 Bitumen (See below) 15 added The grade of bitumen used was made to the following specification:

Solubility in carbon disulfide percent by wt 99 The bitumen was added to the aggregate at a temperature of 380 F. to 400 F., and after mixing was conveyed to the site.

On arrival at the site, a 1' 0" layer of the insulation composition was placed in a 2' 6" wide trench which had been excavated to a depth of 3' 6". The 6" diameter pipeline was located in position, and the final quantity of insulation composition poured to give 1' O covert to the pipeline. The mixture was consolidated by the natural tendency to slump at the elevated pouring temperature, assisted by manual tamping as required. The rate of working was similar to that experienced with cement concrete.

Finally, the trench was backfilled. The pipeline was then ready for operation.

A representative sample was taken of the insulating composition, and was subjected to a thermal conductivity test. The test result showed that the insulation composition had a thermal conductivity of 0.146 B.t.11./ (hr.) (ft. F./ft.). The density was 68.6 lb./ft.

I claim as my invention:

1. An insulating composition consisting essentially of 80-90% by weight of expanded shale particles having a density of 45-60 lbs/ft. admixed with a 20-10% by weight of petroleum asphalt having a ring and ball softening point of 110-285 F.

2. A method for insulating a pipeline comprising the sequential steps:

(1) surrounding the pipeline with an insulating composition consisting essentially of 80-90% by weight of expanded shale particles having a density of 45- 60 lbs/ft. admixed with 20-10% by weight of bi- 4 tumen having a ring and ball softening point of -285 F., the composition being applied at a temperature such that it is plastic; and (2) compacting the insulating composition around the pipeline until the density of the insulating composition is at least equal to the density of water. 3. The method of claim 2 in which the pipeline has previously been coated with bitumen of the same composition as that contained in the insulating composition.

References Cited UNITED STATES PATENTS 2,861,004 11/1958 Sucetti 10688 2,979,415 4/1961 Taylor 25262 2,625,512 1/1963 Powell 106122 2,935,412 5/1960 Gzemsk et al. 106--122 2,977,239 3/1961 Parsons 106122 3,015,626 1/1962 Kingsbury 106281 3,078,324 2/ 1963 Timothy 106281 JULIUS FROME, Primary Examiner J. B. EVANS, Assistant Examiner US. Cl. X.R. 

1. AN INSULATING COMPOSITION CONSISTING ESSENTIALLY OF 80-90% BY WEIGHT OF EXPANDED SHALE PARTICLES HAVING A DENSITY OF 45-60 LBS./FT.3 ADMIXED WITH A 20-10% BY WEIGHT OF PETROLEUM ASPHALT HAVING A RING AND BALL SOFTENING POINT OF 110-285*F.
 2. A METHOD FOR INSULATING A PIPELINE COMPRISING THE SEQUENTIAL STEPS: (1) SURROUNDING THE PIPELINES WITH AN INSULATING COMPOSITION CONSISTING ESSENTIALLY OF 80-90% BY WEIGHT OF EXPANDED SHALE PARTICLES HAVING A DENSITY OF 4560 LBS./FT.3 ADMIXED WITH 20-10% BY WEIGHT OF BITUMEN HAVING A RING AND BALL SOFTENING POINT OF 110-285*F., THE COMPOSITION BEING APPLIED AT A TEMPERATURE SUCH THAT IT IS PLASTIC; AND (2) COMPACTING THE INSULATING COMPOSITION AROUND THE PIPELINE UNTIL THE DENSITY OF THE INSULATING COMPOSITION IS AT LEAST EQUAL TO THE DENSITY OF WATER. 